I’ll cast my vote here to kick off the counterpoint side of this discussion:

Caldwell Lead Sleds are an absolute waste of money which do nothing to develop marksmanship.

Caldwell Lead Sleds are an absurd crutch which falsely make firearms owners believe they can cheat their way into marksmanship.

Caldwell Lead Sleds are commonly misused by unwitting firearms owners to damage their firearms and optics, by use of too much or too little weight, respectively.

If a firearms owner takes 20 shots to zero their rifle, a Lead Sled won’t help them, and it will be exceptionally unfortunate if they DO establish a (false) zero on a Lead Sled, giving them underserved confidence to take their firearm afield. Personally, I zero in 5 rounds, one at 50, one at 100, then a 3 shot group to confirm, using nothing but a bipod and a rear squeeze bag. I’ve been to a dozen or so Rifle Marksmanship courses in the last 20 years, and have taught dozens of students myself in my own NRA Basics of Rifle Shooting, Long Range Rifle, and Precision AR courses in that time as well - I have NEVER heard a single professional instructor, EVER, offer a positive endorsement of items like the Lead Sled.